soot. This is due to a black fungus which jrrows on the "honey 

 dew" excreted by the aphides. This may be produced in such quan- 

 tities as to coat the leayes, and is attractive to various species of ants 

 and wasps frequently to be seen attending the aphides or frequenting- 

 plants infested by them. The black fung-us noted is not in itself 

 especialh' injurious, but it usually indicates the presence of aphides, 



which may ))e 

 the cause of ma- 

 terial injury. 



APHIDES IN 

 GENERAL. 



The insects of 

 the famih^ Aphi- 

 didi<>, or " plant- 

 lice," are espe- 

 cially remarkable 

 on account of 

 their mode of de- 

 yelopment. This 

 will yar}' con- 

 siderably accord- 

 ing- to the species, 

 but at some time 

 in the life of a 

 species true sexes 

 are produced, 

 usual 1 3' in the 

 fall, the sexual 

 female depositing- 

 egg-s after the 

 usual manner of 

 insects. Eg-g-s 

 deposited in the 

 autumn pass the 

 winter in this 

 condition, and 

 their hatching- in 

 the spring- is more 



or less coincident with the revival of growth of vegetation. From 

 the winter eggs Is produced a generation of females, usually wingless, 

 which reproduce agamirally— that is, without the intervention of 

 males, many species, as those under consideration, giving birth to 

 living young. The adult aphides of this first generation are termed 

 "stem-mothers." The oH'spring of the stem-mothers (second gener- 



[Cir.811 



Fig. 1.— Terminal slioot of apple iiiffsttd with the apple aphis (Aphis mali) 

 showing conflition of leaves. (Original.) 



